A variety of technology is known for digitizing handwritten text as the text is written, and for processing of handwritten text data. Typical digitization equipment employs a digitizing tablet which generates data representing the coordinates of a stylus applied to the tablet. Present technology includes digitizing tablets which generate positional information by detecting radio frequency emissions generated by the stylus. The typical stylus of this type may also be provided with an inking tip, and typically further includes a pressure sensor which generates a signal when the stylus is in contact with a surface (a "pen down" signal). This signal may be conveyed to the digitizing tablet by means of a dedicated line or through a secondary radio frequency transmission. By monitoring the pen down signal and the path of the stylus radio emission across a radio-sensitive grid, the digitizing tablet may generate a data stream representing the pen strokes ("strokes") which comprise text written on or in proximity to the surface of the digitizing tablet.
Digitizing tablets are primarily used as input devices for data processing systems. For example, a digitizing tablet and its accompanying stylus may be coupled to a personal computer such that lines traced on the tablet with the stylus are recorded as input to the computer. See, e.g., Tsugei et al., U.S. Pat. No. 4,656,317. It is known to overlay a digitizing tablet with a grid or other form for indicating the proper location on the tablet for entering a particular type of input. See, e.g., Abe, et al., U.S. Pat. No. 4,136,336. It is further known to overlay a display device such as an LCD screen with a transparent digitizing tablet, thus allowing a computer-generated form to be displayed which is visible through the digitizing tablet and allowing the strokes produced by the stylus to be displayed on the display device. See, e.g., Dao et al, U.S. Pat. No. 5,049,862; Ito et al., U.S. Pat. No. 5,177,328.
Present technology further includes the ability to convert stroke data to character strings using a variety of known recognition processes. Generation from stroke data of image data representing a graphical display of the strokes is also known.
With particular regard to integration of digitizing tablets with tasks which are paper-oriented, it is known to combine a digitizing tablet with a scanner, thus allowing a handwritten document to be initially scanned into memory and then altered in memory by input generated by use of a stylus and digitizing tablet. See, e.g., Comerford et al., U.S. Pat. No. 5,243,149. It is also known to overlay the input window of a photocopier with a digitizing tablet such that particular areas of a document may be indicated for copying by circumscribing these areas of the document using the stylus as the document lies on the window. See, e.g., Kishi et al., U.S. Pat. No. 4,745,491.